Rotating transformer for electric resistance seam welding of tubing and the like



July 18, 1961 TUDBURY 2,993,109

ROTATING TRANSFORMER FOR ELECTRIC RESISTANCE SEAM WELDING OF TUBING AND THE LIKE Filed Sept. 11, 1958 2 Sheets-Sheet 1 FIG. 2

INVENTOR.

ATTORNEY CHESTER A. T U DBURY' July 18, 1961 c. A. TUDBURY 2,993,109

ROTATING TRANSFORMER FOR ELECTRIC RESISTANCE SEAM WELDING OF TUBING AND THE LIKE Filed Sept. 11, 1958 2 Sheets-Sheet 2 FIG. 3

INVENTOR.

CHESTER A. TUDBURY FIG. 4

ATTORNEY United States Patent SISTANCE SEAM WELDING OF TUBING AND THE LIKE Chester A. Tudbury, White Plains, N.Y., assignor to The Ohio Crankshaft Company, Cleveland, Ohio, a corporation of Ohio Filed Sept. 11, 1958, Ser. No. 760,339 2 Claims. (Cl. 219-63) This invention pertains to the art of scam welding, and more particularly to a transformer construction for continuously electrically energizing a pair of spaced metallic edges to be progressively welded together.

The invention is particularly applicable to the progressive electric energization of the edges of a C-shaped tube as the edges are brought into electrical contact for the purpose of heating these edges to the welding temperature, and will be described with particular reference thereto, although it will be appreciated that the invention has broader applications.

It is known to provide a rotating type transformer for this purpose, such transformers heretofore being comprised of a multi-turn toroidal primary winding and enclosed by a one turn toroidal secondary having its terminals connected to a pair of coaxial, axially extending sleeve members which in turn connect to a pair of contact discs each having a contact surface on the outer periphery adapted to engage the metal edges to be energized.

A bearing member in close proximity to the discs surrounds the coaxial sleeve and transmits the radial thrusts on the disc to the base of the welding machine.

It has heretofore been conventional to form the coaxial sleeves with an outer diameter substantially less than that of the outer diameter of the toroidal secondary whereby to reduce the required size of the supporting bearing.

Rotating transformers of the type to which this invention pertains deliver secondary currents to the metal edges to be welded of a very substantial magnitude, sometimes being on the order of hundreds of thousands of amperes.

One of the difliculties with previous designs of such rotating transformers has been the current density through the coaxial sleeves. Thus because of their small outer diameter, there is a crowding of the current therethrough which undesirably contributes to increased voltage drop in the transformer and power loss. This construction has been necessary, however, because of the desire to locate the bearings as close to the contact wheels as possible because of the cantilever effect due to the substantial radial pressures on the contact discs in order to obtain a low resistance contact between the contact surfaces thereof and the metal edges to be energized.

The present invention contemplates a new and improved rotating transformer of the general type described which overcomes all of the above-referred to difficulties, and provides a rotating transformer which will have a maximum electrical efficiency and with a minimum current density in the secondary for a maximum power output.

In accordance with the present invention, a rotating transformer of the general type described, is provided comprised of a multi-turn toroidal primary, a one-turn toroidal secondary enclosing the primary, and having a circumferentially extending split effectively located radially beyond the outer periphery of the primary, and with a pair of circumferentially extending contact surfaces one on each side of the split adapted to engage the metal edges to be electrically energized.

Further in accordance with the invention, a shaft extends axially through the secondary in radially supporting relationship thereto, generally and preferably in the plane 2,.i93,l09- Patented July 18, 1961 "ice of the contact edges whereby cantilever-type forces on the transformer are eliminated.

The principal object of the invention is the provision of a new and improved rotating type electrical trans former of the type generally described which is simple in construction, has a maximum electrically efficiency, and which enables a maximum contact pressure to be applied between the contact surfaces and the edges to be energized.

Another object of the invention is the provision of a new and improved rotating type electrical transformer of a general type described wherein rigid supporting means are provided directly in the plane of the contact edges.

Another object of the invention is the provision of a new and improved rotating type transformer of the general type described wherein the current concentrating throat is eliminated.

Another object of the invention is the provision of a new and improved rotating type transformer wherein the length of the current path is the shortest possible.

Another object of the invention is the provision of a new and improved rotating transformer wherein the current in the outer portions of the toroidal secondary flow radially outwardly only to the contact surfaces.

Still another object of the invention is the provision of a new and improved rotating type transformer wherein the supporting bearings can be located in the radial plane through the contact surfaces.

The invention may take physical form in certain parts and arrangements of parts, preferred embodiments of which will be described in this specification and illustrated in the accompanying drawing which forms a part hereof and wherein:

FIGURE 1 is a cross-sectional view of a rotating type transformer in operative relationship with a C-shaped tube, the edges of which are to be welded together, all illustrating a preferred embodiment of the invention;

FIGURE 2 is a view of FIGURE 1 taken approximately on the line 2-2 thereof;

FIGURE 3 is a view somewhat similar to FIGURE 1, but illustrating an alternative embodiment of the invention, and

FIGURE 4 is a view somewhat similar to FIGURE 1 and showing a still further alternative embodiment of the invention.

Referring now to the drawings wherein the showings are believed to be sufficiently complete to enable one skilled in the art of rotating transformers to build and construct a transformer in accordance with the present invention, the figures show a tube 10 having a pair of spaced edges 11 to be welded being advanced from right to left past a pair of rotating contact surfaces 13 on a rotating type transformer constructed in accordance with the present invention. Obviously the edges 11 could be on flat sheets of metal which are to be Welded one to the other, or on tubes of the like having cross-sectional configurations other than round as shown.

The rotating transformer shown is comprised generally of a multi-turn toroidal primary a, and an outer surrounding one turn toroidal secondary b arranged to electrically energize the contact surfaces 13 as will appear. These contact surfaces 13 engage and energize the edges 11 either at the point they are brought together or preferably in advance thereof to cause a welding current to flow therebetween.

The construction of the primary a forms no part of the present invention, and may consist of a coil 20 having a pair of terminal leads 21 extending externally of the transformer to sliprings or the like, not shown. The primary a may also include a magnetically permeable core 23 of any known or desired construction, either of powdered materials or of laminated materials. Usually the material of the core will depend upon the frequency of operation of the transformer. For the lower frequencies, e.g., 60 cycles through 10,000 cycles per second, laminated cores are generally suitable. For frequencies above 10,000 cycles per second, e.g., 450,000 cycles per second, and higher the core 23 will probably be of powdered magnetically permeable materials.

The secondary b completely surrounds and encloses the primary a with the exception of the split 30 defined by close spaced surfaces 31 which in the embodiment of FIGURE 1 are in axially facing relationship. Obviously these surfaces may face otherwise and may extend at an angle relative to the radial plane through the transformer. The secondary b is comprised of a radially inner circumferentially extending portion 33, eircumferentially extending axially end portions 34, and radially outer circumferentially extending portions 35, which in the embodiment of FIGURE 1 is divided into two sections by the split 30. These portions as shown are all in electrically conductive relationship, and are electrically insulated from the coil 2t} by a layer of electrical insulation 37.

Thus alternating currents flowing in the coil 20 will generate a corresponding alternating voltage in the secondary b which voltage appears across the split 30 and is conducted to the contact surfaces 13 through a pair of contact discs 39, one connected to each of the sections of the portion 35 adjacent to the split 30. In the embodiment shown, the surfaces 31 continue outwardly in close spaced relationship on the discs 39 and are separated by electrical insulation 42.

The secondary b and the discs 39 are all shown as being one integral member. Electrically, they are one. Physically, they may be made in several pieces and fastened together, either by brazing, bolting, or otherwise as desired.

In the embodiment of the invention shown, the split 30 is shown as being on the axial center of the secondary b, and thus the primary a. Obviously the split 30 may be located anywhere in the portion 35, as desired.

It is to be noted that with the split located anywhere in the portion 35, its inner radial limit is radially outwardly of the outer surface of the primary a. With this arrangement, the currents from each section 35 flow radially outwardly to the contact surfaces 13, as distinguished from prior constructions where the currents from the outer portion 33 flow radially inwardly usually a distance beyond the mid-circumferentially extending plane of the primary a in order that the currents might be conducted to the axially extending, coaxial sleeves, which sleeve, as before indicated, had a bearing around the outside thereof.

The transformer is mounted for rotation about the axis of the toroid by means of a shaft 50 extending through the central opening of the secondary toroid b defined by the portion 33, and in physical supporting relationship with the secondary b by means of a bearing 52. It will be noted that this bearing is in the radial plane through the contact surfaces 13, and thus any radial forces which are substantial between the tube and the transformer are transmitted directly to the shaft 50'. These forces are then transmitted through the shaft 50 to the base of the machine indicated schematically by the reference character 53. Obviously the shaft 50 may be adjustably mounted relative to the machine 53 in order that various sizes of tube may be accommodated and in order that the pressures between the contact surfaces 13 and the tube 10 may be adjusted. Alternatively, means may be provided for adjusting the vertical height of the tube 10 relative to the transformer. It will be noted that the shaft 50 is mounted relative to the base by supports located axially beyond the plane of the contact surfaces 13, and preferably the shaft 50 is fixed to the base 53 at both ends so as to limit the cantilever effect on the shaft 50. Obviously if the shaft 50 is of sufiicient strength; it need only be supported at one axial end.

It will also be appreciated that power driven means may be provided for rotating the transformer as is conventional in the art. Alternatively, the tube 10 may be driven in the direction shown in FIGURE 2 by other power means, and the transformer simply rotates because of the contact pressure between the surfaces 13 and the edges 11.

FIGURE 3 shows an alternative embodiment of the invention. In this figure the secondary b is comprised of an inner portion 33', right and left hand end portions 34', and outer portion 35', all much similar in construction to that shown in FIGURE 1. The outer portion 35, however, has at one axial end an outwardly extending flange having fixed to its axial end a contact disc 61 having on the outer periphery thereof a contact surface 13. The inner periphery 63 of the disc 61 is generally coextensive with the inner periphery of the portion 35' and is in spaced relationship with an outer peripheral surface on the right hand end portion 34 to form the split 66. A second contact disc 68 is bolted to the axial end of the right hand end portion 34' and extends outwardly in axially spaced relationship to the disc 61 and has its outer periphery forming the other contact surface 13, the split 66 being continuous with the space between the disc 61, 68, as is shown. In this embodiment, it will be noted that the split 66 is again radially outwardly of the outer periphery of the primary :1 so that the currents from the portion 35' flow radially outwardly to the contact surface 13.

In this embodiment of the invention, the transformer rotates with the shaft 50, which shaft, as shown, has an outer diameter generally equal to the inner diameter of the portion 33 and the shaft 50 is rotatably supported in bearings 70 in turn supported on the base of the machine.

Again it will be noted that a transformer is rotatably supported on a radial plane through the contact surfaces 13.

If desired, the discs 61, 68 may be bolted together by means of bolts 72 electrically insulated, preferably from both discs as is conventional in the art. In this manner, radial forces on the contact surfaces 13 of the disc 61 are transmitted directly to the disc 68 and thence to the shaft 50'.

FIGURE 4 shows a still further alternative embodiment of the invention which while not as preferred as that of FIGURES l and 3, still embodies the principles of the invention. Thus, in FIGURE 4 the secondary b is comprised of an inner portion 33", end portions 34", and an outer portion 35". In the embodiment of the invention shown, however, the right hand end portion 34" has an axially and circumferentially extending split 75 which in effect divides the portion 34" into an inner section 76 and an outer section 77, between which the voltages induced in the secondary b appear. A disc 78 is bolted to the axial end of the section 77 and has an outer peripheral extending contact surface 13. A second contact disc 79 is bolted to the axial end of the innermost section 76, and extends in spaced insulated relationship radially outwardly to the peripheral extending contact surface 13. Electrical insulation 80 is provided in the space.

In FIGURE 4 the split 75 is thus located radially inwardly of the outer peripheral surface of the primary a. At the lower frequencies, such a construction will generally not be objectionable because the currents can flow radially outwardly from the outer portion 35" to the disc 78 and the contact surface 13. However, as the frequencies increase, normally such a construction would be undesirable because of the surface or skin effect where the currents would tend to flow radially inwardly along the surface of the section 77 to the split 75, and thence radially outwardly through the disc 78. It will be noted that with the construction shown in FIGURE 4, the split 75 is effectively located as to be radially'beyond the outer periphery of the primary a at least for the lower frequencies.

In this embodiment of the invention, the shaft 50 is mounted as is the shaft of FIGURE 1, and the bearing 52 is located in an axial recess on the inner portion of the disc 79, but again in the radial plane through the contact surfaces 13.

It will be appreciated that the radial spacing of the contact surfaces '13 from the outer portion 35 may be as desired, either more or less than that shown in the figures. in fact, with the construction shown, the contact surfaces 13 may be formed directly in the outer surfaces of the outer portion 35 if desired. By employing the discs shown, however, a substantial radial rigidity is obtained which facilitates in distributing the radial forces on the transformer, and in transferring them to the shaft 50.

Thus, in all cases it will be noted that the split of the secondary b is effectively located beyond the radial outer periphery of the primary a such that the currents flowing from the outer portion 35" of the secondary b may always flow in a radially outward direction. Furthermore, it is to be noted that the radial forces on the contact surfaces 13 are opposed by supporting members located directly in the radial plane through these contact surfaces using either or both features, a very substantial improvement in operation results.

The invention has been described relatively schematically, it being appreciated that various means may be employed to remove the heat generated within the transformer, all as is conventional within the art, and that the primary 20 may have any desired number of turns and that the electrical energy may be conveyed to the terminal leads 21 in any desired manner. Obviously the exact dimensioning of the various parts will depend upon the physical forces involved, and the magnitude of the electrical currents to be carried.

The invention has been described with reference to preferred embodiments. Obviously modifications and alterations will occur to others upon a reading and understanding of this specification, and it is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. A rotating transformer for electrically energizing metallic edges to be welded, said transformer comprising a pair of generally circular members in spaced insulated relationship and adapted to be at different voltage potentials, said members having peripherally extending contact surfaces on the outer edge thereof, a shaft member extending transversely through said members and a bearing member in relative supporting relationship with said members and shaft in the radial plane through said contact surfaces.

2. A rotating transformer comprising a toroidal primary, a one-turn toroidal secondary enclosing said primary, said secondary including an electrically conductive radially inner portion extending across the inside periphery of the primary, electrically conductive end portions extending across the ends of the primary, and an electrically conductive radially outer portion extending across the outside periphery of the primary, said secondary having a circumferentially extending slit therein, contact members connected at their radially inner ends to the secondary on opposite sides of said slit and extending radially outward in closely spaced relationship to one another and having closely spaced contact surfaces on their radially outer ends, a rotary shaft extending through the secondary at said radially inner portion thereof, and rotary bearing means on said shaft engaging and supporting the secondary in line radially with said contact surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 1,199,537 Fulda Sept. 26, 1916 1,478,262 Snodgrass et a1 Dec. 18, 1923 1,862,642 Von Henke June 14, 1932 2,561,739 Hunter July 24, 1951 

